Method and apparatus for cutting grooves in a bore

Abstract

A broaching tool, comprising a shank, a body and a cutting head that comprises at least one rake face. The rake face comprises a cutting edge that comprises a cutting corner at a forward end of the cutting head. The rake face is configured such that upon simultaneously rotating the broaching tool about the axis of the broaching tool and advancing the broaching tool along the axis of the broaching tool in a forward direction, the first corner travels in a first circular helix pattern. Also, a method of forming one or more grooves in a bore-containing structure, the method comprising simultaneously rotating a broaching tool and a bore-containing structure relative to one another about the axis, and moving the broaching tool and the bore-containing structure relative to one another along the axis. Also, methods of making broaching tools, and broaching machines.

1 . A broaching tool for rifling a gun barrel comprising:
 a shank;   a body;   a cutting head;   an axis of said broaching tool extending from a rearward end of said broaching tool at said shank to a forward end of said broaching tool at said cutting end, said axis extending through said shank, said body and said cutting head;   said body positioned forward relative to said shank;   said cutting head positioned forward relative to said body;   said cutting head comprising at least a first rake face, said first rake face comprising a first cutting edge,   said first cutting edge comprising a first cutting corner at a forward end of said cutting head;   said first rake face configured such that upon rotating at least one of said broaching tool and said gun barrel about said axis of said broaching tool and advancing said tool along said axis of said broaching tool in a forward direction relative to said gun barrel, said first corner travels in a first circular helix pattern, each point on said first circular helix pattern spaced from said axis of said broaching tool by a distance that is greater than a distance that any point on said shank or said body is spaced from said axis of said broaching tool.   
     
     
         2 . A broaching tool as recited in  claim 1 , wherein:
 said cutting head comprises at least two rake faces;   said at least two rake faces each comprising a respective cutting corner at said forward end of said cutting head.   
     
     
         3 . A broaching tool as recited in  claim 2 , wherein said respective cutting corners of said at least two rake faces substantially uniformly spaced about said forward end of said cutting head. 
     
     
         4 . A broaching tool as recited in  claim 2 , wherein:
 said first cutting corner and said second cutting corner are located on an imaginary substantially circular pattern, said imaginary substantially circular pattern is in a plane perpendicular to said axis of said broaching tool, a spacing between said first cutting corner and said second cutting corner on said imaginary substantially circular pattern is in a range of from 115 degrees to 125 degrees.   
     
     
         5 . A broaching tool as recited in  claim 1 , wherein:
 said cutting head further comprises a second rake face and a third rake face;   said second rake face comprises a second cutting edge;   said second cutting edge comprises a second corner at said forward end of said cutting head;   said second rake face is configured such that upon rotating said broaching tool about said axis of said broaching tool and advancing said broaching tool along said axis of said broaching tool in a forward direction, said second corner travels in a second circular helix pattern, each point on said second circular helix pattern spaced from said axis of said broaching tool by a distance that is greater than said distance that any point on said shank or said body is spaced from said axis of said broaching tool,   said third rake face comprises a third cutting edge,   said third cutting edge comprises a third corner at said forward end of said cutting head,   said third rake face is configured such that upon rotating said broaching tool about said axis of said broaching tool and advancing said broaching tool along said axis of said broaching tool in a forward direction, said third corner travels in a third circular helix pattern, each point on said third circular helix pattern spaced from said axis of said broaching tool by a distance that is greater than said distance that any point on said shank or said body is spaced from said axis of said broaching tool.   
     
     
         6 . A broaching tool as recited in  claim 1 , wherein:
 said broaching tool further comprises a pilot portion,   each point on said pilot portion is spaced from said axis of said broaching tool a distance that is less than a distance that each point on said first circular helix pattern is spaced from said axis of said broaching tool.   
     
     
         7 . A broaching tool as recited in  claim 6 , wherein said pilot portion extends farther in said forward direction than any other part of said broaching tool. 
     
     
         8 . A broaching tool as recited in  claim 1 , wherein said cutting head is removable from said body. 
     
     
         9 . A broaching tool as recited in  claim 8 , wherein:
 said cutting head has a region with external threads,   said body has a region with internal threads, and   said external threads of said cutting head are capable of being screw-threaded into said internal threads of said body.   
     
     
         10 . A broaching tool as recited in  claim 8 , wherein:
 said body has a region with external threads,   said cutting head has a region with internal threads, and   said external threads of said body are capable of being screw-threaded into said internal threads of said cutting head.   
     
     
         11 . A broaching tool as recited in  claim 1 , wherein said body is removable from said shank. 
     
     
         12 . A broaching tool as recited in  claim 11 , wherein:
 said body has a region with external threads,   said shank has a region with internal threads, and   said external threads of said body are capable of being screw-threaded into said internal threads of said shank.   
     
     
         13 . A broaching tool as recited in  claim 1 , wherein:
 said shank comprises at least a shank first ramp portion,   in a sequence of at least first through tenth shank imaginary planes that are perpendicular to said axis of said broaching tool and that are spaced evenly, respective dimensions of said shank first ramp portion decrease as said distance from said cutting head increases.   
     
     
         14 . A broaching tool as recited in  claim 1 , wherein:
 said body comprises at least a body first ramp portion,   in a sequence of at least first through tenth body imaginary planes that are perpendicular to said axis of said broaching tool and that are spaced evenly, respective dimensions of said body first ramp portion increase as said distance from said cutting head increases.   
     
     
         15 . A broaching tool as recited in  claim 1 , wherein said shank comprises at least a first indexing region. 
     
     
         16 . A broaching tool as recited in  claim 15 , wherein said first indexing region comprises at least first and second indexing surfaces at a rear face of said shank, and said first and second indexing surfaces are non-co-planar. 
     
     
         17 . A broaching tool as recited in  claim 15 , wherein said indexing region comprises at least a first groove. 
     
     
         18 . A broaching tool as recited in  claim 15 , wherein said indexing region comprises at least a first rib. 
     
     
         19 . A broaching tool as recited in  claim 15 , wherein said indexing region comprises at least a first non-cylindrical, non-conical, non-frustoconical recess. 
     
     
         20 . A broaching tool as recited in  claim 15 , wherein said indexing region comprises at least a first non-cylindrical, non-conical, non-frustoconical protrusion. 
     
     
         21 . A broaching tool as recited in  claim 15 , wherein said indexing region comprises at least two protrusions. 
     
     
         22 . A broaching tool as recited in  claim 15 , wherein said indexing region comprises at least two recesses. 
     
     
         23 . A broaching tool as recited in  claim 15 , wherein said indexing region comprises at least one protrusion and at least one recess. 
     
     
         24 . A method of forming one or more grooves in a bore-containing structure, said method comprising: rotating at least one of a first broaching tool and a bore-containing structure relative to one another about a first axis, said first broaching tool and said bore-containing structure aligned such that said first axis is an axis of said first broaching tool and an axis of a bore in said bore-containing structure, and moving said first broaching tool and said bore-containing structure relative to one another along said first axis;
 so that a cutting head of said first broaching tool cuts at least a first groove pattern in said bore-containing structure around said bore, said first groove pattern comprising at least a first circular helix relative to said first axis;   said first broaching tool, comprising:   a shank;   a body; and   said cutting head;   said axis extending from a rearward end of said first broaching tool to a forward end of said first broaching tool through said shank, said body and said cutting head;   said body is forward relative to said shank;   said cutting head is forward relative to said body;   said cutting head comprises at least a first rake face;   said first rake face comprises a first cutting edge;   said first cutting edge comprises a first corner at a forward end of said cutting head.   
     
     
         25 . A method as recited in  claim 24 , wherein said moving said first broaching tool and said bore-containing structure relative to one another along said first axis causes said first broaching tool to move forward relative to said bore-containing structure. 
     
     
         26 . A method as recited in  claim 24 , wherein:
 said cutting head comprises at least two rake faces, including said first rake face,   each rake face comprises a respective cutting corner at said forward end of said cutting head, and   said respective cutting corners of said at least two rake faces are substantially uniformly spaced on said forward end of said cutting head.   
     
     
         27 . A method as recited in  claim 24 , wherein:
 said cutting head further comprises a second rake face and a third rake face,   said second rake face comprises a second cutting edge,   said second cutting edge comprises a second corner at said forward end of said cutting head,   said third rake face comprises a third cutting edge,   said third cutting edge comprises a third corner at said forward end of said cutting head, upon said rotating said first broaching tool and said bore-containing structure relative to one another about said first axis, and said moving said first broaching tool and said bore-containing structure relative to one another along said first axis, said second cutting edge cuts a second groove pattern in said bore-containing structure around said bore, and said third cutting edge cuts a third groove pattern in said bore-containing structure around said bore, said second groove pattern a second circular helix relative to said first axis, said third groove pattern a third circular helix relative to said first axis, said second circular helix axially offset relative to said first circular helix, said third circular helix axially offset relative to said first circular helix and relative to said second circular helix.   
     
     
         28 . A method as recited in  claim 24 , wherein:
 said first broaching tool further comprises a pilot portion,   said pilot portion extends farther in said forward direction than any other part of said first broaching tool, and   upon said moving said first broaching tool and said bore-containing structure relative to one another along said first axis, said pilot portion enters said bore prior to said cutting head of said first broaching tool cutting said first groove pattern in said bore-containing structure.   
     
     
         29 . A method as recited in  claim 24 , wherein:
 said method further comprises:   rotating said first broaching tool and said bore-containing structure relative to one another about said first axis, said first broaching tool and said bore-containing structure aligned such that said first axis is an axis of said first broaching tool and an axis of a bore in said bore-containing structure, and   moving said first broaching tool and said bore-containing structure relative to one another along said first axis,   so that said cutting head of said first broaching tool cuts at least a second groove pattern in said bore-containing structure around said bore, said second groove pattern comprising at least one circular helix relative to said first axis.   
     
     
         30 . A method as recited in  claim 29 , wherein said method further comprises indexing said first broaching tool relative to said bore-containing structure prior to said rotating said first broaching tool and said bore-containing structure relative to one another about said first axis, and moving said first broaching tool and said bore-containing structure relative to one another along said first axis. 
     
     
         31 . A method as recited in  claim 30 , wherein coils of said second groove pattern are offset axially from coils of said first groove pattern by a distance equal to from 45% to 55% of a shift of said first groove pattern. 
     
     
         32 . A method as recited in  claim 30 , wherein coils of said second groove pattern are offset axially from coils of said first groove pattern by a distance outside said range of from 45% to 55% of a shift of said first groove pattern.